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  • 2014 Volume 34 Issue 11
    Published: 15 November 2014
      
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  • Finite Element Simulation on Acoustic Measurement of the Infurnace Temperature Field
    LI Yanqin,JI Huidong,ZHOU Junjie,CAO Hailiang,ZHONG Wei,ZHOU Huaichun
    2014, 34(11): 837.
    Abstract ( )   Knowledge map   Save
    With the twodimensional Gaussian model built according to features of typical temperature field in a tangential furnace, the propagation of a pulse acoustic wave in the temperature field was simulated with software Comsol  based on the theory of wave equation, during which visualization of the acoustic wave fronts inside the field was achieved, while the propagation time was calculated using crosscorrelation method. For verification purposes, a model based on the principle of sound ray was developed and fundamentally tested, with which the distribution of acoustic wave paths was determined and the theoretic sound propagation time was calculated by integration method. Results show that the propagation time in the temperature field simulated with waveequation model appears a bit longer than theoretic solutions. The errors are generally below 1% in the simulation, which are resulted from pseudo forward offset of sound source signals, and the minor the mesh or the higher the temperature is, the more the pseudo offset will be.
  • Study on Location of Water Wall Tube Leakage Based on Acoustic Array
    SHEN Guoqing,ZHANG Shiping,AN Liansuo,LI Gengsheng,GAO Xianbo
    2014, 34(11): 843.
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    By arranging measurement points of acoustic pyrometer and introducing acoustic array orientation technique, simultaneous monitoring of furnace temperature and detection of leak acoustic signals can be achieved so as to accurately loacte the leakage position on water wall tubes. Based on the acoustic array orientation model newly built for tube leakage detection, a 3D orientation simulation was performed using time difference of arrival (TDOA) method and improved Chan algorithm, and subsequently experimental studies were conducted respectively under open and furnace environment. Results show that both the simulation and experimental results meet engineering requirements, which prove the method to be feasible.
  • Numerical Study on Sound Transmission Through Boiler Tube Arrays Based on Phononic Crystal Theory
    JIANG Genshan,LIU Yuechao,AN Liansuo
    2014, 34(11): 850.
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    To study the effects of tube array arrangement on the sound transmission in boiler heat exchangers, the band gap width of transmitted wave after tube arrays in inline and staggered arrangement was calculated and verified respectively using Matlab and Comsol software, based on phononic crystal theory, by reasonably setting the longitudinal pitch, transverse pitch and size of the tube array as well as the environmental temperature. Results show that after sound passing through tube arrays, acoustic band gap will be produced, and the center frequency of first band gap in TX direction has relations to the tube array structure and the environmental temperature; the band gap width is related to the filling rate, and generally the sound transmission property under staggered arrangement is worse than under inline arrangement; for a fixed filling rate, the frequency of sound insulation under staggered arrangement is higher than inline arrangement; the width of first band gap increases with rising filling rate under inline arrangement, and the largest width of band gap appears under staggered arrangement at the filling rate of 0.38; the sound insulation effect under staggered arrangement is better than inline arrangement in a filling rate range below 0.23.
  • Pressure Characteristics of Helmholtztype Valveless Selfexcited Pulse Combustor with Bend Tail Tube
    XU Yanying,ZHAI Ming,DONG Peng2,ZHU Qunyi
    2014, 34(11): 856.
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    An experimental system was set up for the Helmholtztype valveless selfexcited pulse combustor with bend tail tube, so as to study the effects of following factors on the pressure oscillation characteristics in the combustor, such as the tail tube structure parameters, the heat load and the excess air ratio, etc. Results show that the pulse combustor with bend tail tube can produce stable pulse combustion with relative high oscillation amplitude and low oscillation frequency, in a waveform shape approximate to sine curve. The average value and amplitude of pressure reduces along expanded length direction of the 90° bend tail tube, and the pressure distribution is similar to that of a quarter wave tube. The pressure amplitude decreases with the rise of bending angle, and the amplitude corresponding to the case with bending position at the exit of tail tube is smaller than the case with bending position at the entrance. For a fixed structure of combustor, the pressure amplitude increases with the rise of both heat load and excess air ratio. The experimental results show qualitative agreement with theoretical calculation values.
  • Analysis on Offdesign Flow Field in Highpressure Combined Valve of a 600 MW Steam Turbine
    YU Jingmei,MENG Fandan,LIU Panpan,YU Yanhong,CHEN Cheng,ZHANG Xing
    2014, 34(11): 862.
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    The flow field in highpressure combined valve of a 600 MW steam turbine was analyzed by numerical simulation, of which the flow characteristics were studied by solving the 3dimensional NavierSrokes equations using a k ε  turbulence model. The flow field was numerically simulated with the main stop valve in fully open position and the governing valves opened in different sequences, so as to further analyze the mechanism of flow loss. Results show that the flow rate of governing valve B is larger than governing valve A, and the former has a better flow state than the latter. Small pressure loss of each section and good flow state of each valve can be achieved by opening valve B in prior to valve A.
  • Application of Reversed Modeling Method in Prediction of Steam Turbine Heat Rate
    LIU Chao,NIU Peifeng,YOU Xia
    2014, 34(11): 867.
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    To investigate the nonlinear relationship between steam turbine heat rate and the affecting factors, a reversed modeling method was proposed for the heat rate based on adaptive chaotic oppositionbased learning gravitational search algorithm (ACOGSA) and least squares support vector machine (LSSVM), following which a heat rate prediction model was established with operation data of a 600 MW supercritical steam turbine unit using LSSVM reversed modeling method. ACOGSA algorithm was used to solve the problem of LSSVM optimal parameters, and the prediction results were compared with those of the GSALSSVM model and BP neural network model. Results show that the proposed model has better generalization ability than traditional models, which therefore can predict the heat rate of steam turbine more accurately.
  • A Measurement Method for Surface Temperature and Emissivity of Metallic Materials
    ZHANG Xiangyu,SUN Yipeng,XIANG Xiaofeng,ZHANG Bo,XU Hongjie
    2014, 34(11): 873.
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    A noncontact measurement method for surface temperature and emissivity of hot metals was proposed based on radiation image thermometry revised by spectral emissivity. Firstly, the curve of monochromatic emissivity along with wavelength was calculated according to spectrum information captured by spectrometer from a hot metallic surface. Then the temperature distribution and emissivity were calculated by colorimetric analysis based on the red and green monochromatic radiation intensity distribution through colour images taken by visible light CCD camera, in combination with the corrected monochromatic emissivity curve. The accuracy of the proposed method was verified by experimental tests for a hot billet. Results show that the measurement can truly reflect the billet surface temperature distribution and give the uneven heating information, which therefore can be used to guide the improvement of relevant heating processes.
  • Capture of CO2 by ［NH2pmim］Br Ionic Liquid at Normal Temperature and Pressure
    ZHAO Yi,LI Qiangwei,WANG Lidong,YANG Lijuan
    2014, 34(11): 878.
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    To capture the CO2 emitted from coal combustion, ionic liquid 1(1aminopropyl)3methylimidazole bromine (expressed as ［NH2pmim］Br) containing —NH2 functional groups was synthesized by taking Nmethylimidazole as the main material, of which the CO2 absorption capacity was studied at normal temperature and pressure before and after regeneration. Moreover, comparative experiments were conducted between ［NH2pmim］Br and ［bmim］Br to investigate the effects of piperazine on CO2 absorption by ［NH2pmim］Br. Results show that the introduction of amino increases the absorption capacity to CO2 and the synthetic ionic liquid still has relatively high CO2 absorption capacity after regeneration; piperazine promotes the CO2 absorption reaction of ［NH2pmim］Br; the absorption capacity of ［NH2pmim］Br is far greater than ［bmim］Br, due to the existence of —NH2, which may make both the chemical and physical absorption of CO2 happen simultaneously.
  • Effects of Collector Radius and Turbine Pressure Drop on Performance of a Solar Chimney System
    YAN Yunfei,DAI Changlin,ZHANG Li
    2014, 34(11): 884.
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    To study the effects of collector radius and turbine pressure drop on power output of a solar chimney system, numerical analysis was carried out to temperature distribution in the collector along the flow direction. Results show that there exists an optimum turbine pressure drop, in which case the corresponding system power output is the highest. Under a fixed turbine pressure drop, the system power output increases with rising collector radius, however, when the collector radius rises to a certain size, the system output will not increase anymore. Simultaneously, the growth of turbine pressure drop would accelerate the rate of temperature rise, improve the final temperature of air stream and reduce the work potential of the system. Above analysis results may serve as a reference for engineering application of solar chimney systems.
  • Analysis on Dynamic Characteristics of Offshore Wind Turbines with Generator Faults
    AN Liqiang,SUN Shaohua,ZHOU Xingyin
    2014, 34(11): 891.
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    Taking the offsore wind turbine as an object of study, operation process of the wind turbine was simulated based on the model set up with FAST software by taking the turbulent wind and random waves as input conditions and considering the impact of gravity load, aerodynamic load, inertia load and wave load. Meanwhile, the effect of pitch rate on load of the wind turbine with generator faults was also studied. Results show that generator faults would cause great damage to turbine blades, when great change of axial force happens at blade root due to the increase of inertial force, where maximum force is generated. The pitch rate has a significant impact on tip displacement when active pitchtofeather control is used during blade unloading.
  • Experimental Study of a Fluidized Bed Electrod Direct Carbon Fuel Cell
    ZHANG Jubing,PIAO Guilin,XIE Hao,YANG Hongmin
    2014, 34(11): 897.
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    By applying the fluidized bed electrode to direct carbon fuel cell, a novel fluidized bed electrode direct carbon fuel cell (FBEDCFC) was developed. To study the output properties of the FBEDCFC, an annular experimental facility was set up, based on which the effects of following factors on the discharge curves were analyzed, such as the reaction temperature, cathode/anode gas flow, nickel catalyst content and carbon particle size, etc. Results show that the open circuit voltage and maximum output power density of respectively 0.896 V and 28.70 mW/cm2 can be reached by the FBEDCFC, under the conditions of reaction temperature at 923 K, anode gas flow of 18.59 mm/s, cathode gas flow of 19.57 mm/s, nickel catalyst content of 45 g and carbon particle size in 2.53.5 mm.
  • Comprehensive Analysis of a Multipurpose Heating System with Dragging and Heating Cogeneration
    XU Zelin,JIANG Yanni,YIN Peiguang,HAO Yazhen
    2014, 34(11): 903.
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    To solve the problem of low exergy efficiency of heat supply unit retrofitted from condensing unit with large capacity and less heat supply, a multipurpose heating system with dragging and heating cogeneration was proposed, which enables small steam tubine to recover its waste heat for heating purpose in winter, and recycle the heat to condensate system in summer, so as to raise the amount of lowpressure recuperative steam and improve the thermal economy of recuperative system. Taking the underfloor heating mode as an example, a comparison was made with the heating unit retrofitted from conventional condensing unit. Results show that before retrofit, the exergy efficiency of the heater for heating network is only 20.27%, and after retrofit, the exergy efficiency of hightemperature heater is raised to 52.31% and that of lowtemperature heater is raised to 71.89%. The average temperature of heating steam is reduced by 205.42 K, and the temperature difference for heat transfer is decreased by 207.85 K, compared to conventional heating mode. The coal consumption is reduced by 4.54 g/(kW·h) in heating period, while the relative heat loss is reduced by 16.82 kJ/(kW·h) in nonheating period. The conversion loss is reduced by 9%, and the comprehensive coal consumption for power supply is reduced by 1.06 g/(kW·h), indicating obvious energy saving effect.
  • Influence of Thermodynamic Model on Simulation Results of 2D Flow Field in an ORC Turbine Nozzle
    HAN Zhonghe,WU Weiming,WANG Zhi
    2014, 34(11): 909.
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    To study the real aerodynamic characteristics of organic working fluid, the fluid thermodynamic parameters were calculated using 3 gas equations of state with different precisions. Considering the viscosity of working fluid, numerical investigation was conducted to a 2D ORC turbine nozzle, during which the aerodynamic parameters, mass flow and outlet flow angle of working fluid inside the turbine nozzle were analyzed based on different gas equations of state. Results show that the calculation value obtained with ideal gas equation is quite different from that with real gas equation. It is recommended to design ORC turbines based on the equation of state of real gas.
  • Feasibility Analysis and Calculation on Initial Startup of an AP1000 Nuclear Power Unit with Nonnuclear Steam
    GAO Zhiqing，ZHU Fengyao
    2014, 34(11): 915.
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    An integrated calculation and analysis were conducted on thermal balance of available steam accumulation generated by primary circuit and steam energy demanded by initial startup of secondary circuit before fuel rod loading of an AP1000 nuclear power unit. Results show that the AP1000 nuclear power unit can supply adequate quantity and high quality of nonnuclear steam to drive and maintain the rotation of its turbinegenerator set for certain time at rated speed; it is feasible for the AP1000 nuclear power unit to complete its first startup with nonnuclear steam.